The present invention relates to a field emission device which can facilitate the formation of a micro-tip for emitting electrons by a field effect.
As an image display device which can replace the existing cathode ray tube of a television set, the flat panel display has been under vigorous development for use as an image display device for wall-mounted (tapestry) televisions or high definition televisions (HDTV). Such flat panel displays include liquid crystal devices, plasma display panels and field emission devices, among which the field emission device is widely used due to the quality of its screen brightness and low power consumption.
The structure of a conventional vertical field emission device will now be described with reference to FIG. 1.
The vertical field emission device includes a rear glass substrate 1, a cathode 2 formed on rear glass substrate 1, a field emission micro-tip 4 formed on cathode 2, an insulation layer 3 formed on cathode 2, and having a hole 3' for surrounding micro-tip 4, a gate 5 formed on insulation layer 3 and having an aperture 5' for allowing electron emission by a field effect from micro-tip 4, an anode 6 for pulling electrons emitted from micro-tip 4 so as to impinge onto a fluorescent layer 7 with proper kinetic energy, and a front glass substrate 10 having fluorescent layer 7 deposited thereon and anode 6 formed in a striped pattern.
Also, as shown in FIGS. 2A and 2B, a conventional horizontal field emission device has a structure such that cathode 2 and anode 6 are parallel with substrate 1 so as to emit electrons in parallel with substrate 1, unlike the vertical field emission device shown in FIG. 1.
As shown, an insulation layer 3 is formed on a glass substrate 1, and a cathode 2 and an anode 6 are deposited on an insulation layer 3. A hole 3' of a proper depth is formed on insulation layer 3 disposed between cathode 2 and anode 6, and a gate electrode 5 is provided within hole 3', for controlling the electron emission from cathode 2 to anode 6.
However, in the vertical field emission device using the single tip as shown in FIG. 1, since the flow of electron beams is determined depending on the size of aperture 6' of the gate, a technique for forming a micro-tip of several tens of nanometers is necessary. That is to say, since a highly precise fabrication process of a submicron unit is required for forming the gate aperture depending on the tip size (diameter) and the gate aperture size, there are problems in the process uniformity and the yield in the case of application to a large device. Also, in forming the micro-tip, if the aperture becomes larger, the level of the gate bias voltage becomes higher, thereby necessitating a high voltage.
The horizontal field emission device shown in FIG. 2A has a high yield and a uniform structure in fabrication thereof in contrast with the vertical field emission device. However, the horizontal field effect makes the various applications of electron beam emission difficult. That is to say, since the flow of electron beams is extremely limited to an identical horizontal plane, it is very difficult to apply electron beams.